1. Field of the Invention
The present invention relates to a method of automatically controlling photographic exposure and focussing based upon a main object, a camera realizing this method, and a photographic printing method. More particularly, the invention relates to a method of automatically detecting a main object within a scene to be taken, and determining a taking exposure amount and main object distance in accordance with the detected main object, and a camera realizing this method. The invention further relates to a method of producing a photographic print having a proper density of the image of a main object, by using a photographic film taken on the basis of photo-taking information of the main object.
2. Description of the Related Art
Conventional automatic focussing cameras are of a one-point distance measuring type and a multi-point distance measuring type. For the former type, one measuring point is set at the center of a scene to be taken, and this one measuring point is represented by a target mark within a viewfinder. Framing of the camera is determined so that part of a main object selected as desired among various objects in a scene is set within the target mark of the viewfinder at the center of the viewfinder. After this framing, the release button is half depressed to measure the distance to the main object within the target mark. Upon full depression of the release button, the focus of the taking lens is set to the measured main object distance and the shutter is activated to photograph the scene. An original fame of the scene image is created on a photographic film such as a color negative film. In photographing a focussed main object located out of the central area of a scene by using a camera of the one-point distance measuring type, it is necessary to provide a focus lock in order to focus the main object. In operation of the focus lock, first a main object is located at the target mark and the release button is half depressed to measure the distance to the main object. Next, the camera is pointed at a different area to determine a desired framing of the scene while maintaining the half depression of the release button, and thereafter it is fully depressed.
For the multi-point distance measuring type, a plurality of measuring points are provided for one scene, and the distance measuring is accomplished for each point. A plurality of object distances are obtained, one of which is selected as main object distance for focussing the taking lens. Of a plurality of distances as measured, the shortest object distance is commonly used as the main object distance from an empirical rule that the main object is located on the near distance side. For the multi-point distance measuring type, there are ordinarily about 5 distance measuring points at most, and they are set only at the central area of a scene in the horizontal direction. Therefore, if a main object is located outside of the measuring point area, a focus lock becomes necessary to properly focus the scene.
Both the one-point and multi-point distance measuring types, require cumbersome operations of the focus lock, and, therefore, good photographs might be missed in some cases. Since the multi-point distance measuring type uses the method of near distance priority, the taking lens will be focused to any object in front of the main object, resulting in improper focussing. Furthermore, if the taking exposure is controlled on the basis of the brightness of a main object, the brightness of an object determined incorrectly as the main object would be erroneously used for the taking exposure control.
There is also known a camera of the type wherein a reflected light from a scene illuminated by a flash light during flash photographing is measured, and the taking exposure is controlled by an integrated value of reflected light beams. With a camera of this type, if an object having an extremely high reflectance is located near a main object, it is not possible to properly expose the main object because of the high amount of reflected light from the object near the main object.
With a conventional photographic printing method, an elementary printing exposure amount is determined by an average density, e.g., LATD (Large Area Transmittance Density), of an original frame of a photographic film. A print correction amount is calculated according to the characteristic feature, e.g., rear light scene, extracted from the original frame. The elementary printing exposure amount is corrected using the calculated print correction amount. Using the corrected printing exposure amount, the original frame is printed on a photographic paper. If the density is for different from the LATD, it is necessary to determine the print correction amount from the density of the main object image, so as to the image at a proper printing exposure amount. However, the density of the main object image cannot be estimated correctly because the position of the main object image within the original frame is unknown. In particular, if the position of the main object image is not at the central area of the original frame, it is difficult to estimate the density of the main subject image. This lowers the correction precision of the printing exposure amount.
Automatic exposure control systems for camera have become highly precise, and so the image of a main object can be photographed on a photographic film at a proper density. It is therefore often possible to print the image of a main object on a photographic paper at a proper density, without measuring the density of the original frame, only by supplying a printing exposure time preset for each type of a photographic paper and each printing magnification. However, if the density of a main object image is far different from the LATD, this image cannot be printed at an optimum density when such a preset printing exposure time is used.